The present invention relates to an arrangement for changing the lever ratio of a two-armed rocker lever, particularly for the transfer movements in a press. The rocker lever is pivotally connected in a lever arm and the starting movement is capable of being tapped by another lever arm. This lever arm comprises a slide guide for the rocking bearing of the rocker lever as well as a control device and rotation transmission devices and a nutspindle connection for the sliding movement of the slide guide relative to the rocker lever.
Arrangements of the above-described type are known. Thus, the German Patent Document DE-PS 959 783 shows flying shears for subdividing moving material that is to be cut, and in which the length of the section can be changed at any speed of the material to be cut. While the cutting-moving characteristic remains the same, the travelling-along speed of the blades must be adaptable. This is achieved in that the drive of one of the blades takes place by means of a thrust crank with a slide guide. The guide parts can be adjusted with respect to the driving crankshaft, and a new lever ratio can be adjusted for the thrust crank by means of a spindle-nut connection. The spindle is disposed on the frame side.
From the European Patent Document EP 0 202 882 A2, a moving drive for the transfer movements in a press is known in which the above-mentioned possibilities were not taken into account. On the contrary, the adjusting devices for changing the lever ratios of a rocker lever are disposed in this rocker lever and must be moved when the rocker lever carries out a rocking motion. In this case, two rocker levers respectively are provided for each axis of movement for the moving of workpieces through the processing stages of the press. By means of a cam follower roller, each of the rocker levers is put against a rotating cam, the profile of which determines the rocking motion of the rocker lever and thus the stroke length in the axes of movement. The tapping point for the transfer movement at each rocker lever can be adjusted by means of a nut-spindle connection. The automating of the adjustment takes place by means of one motor operator respectively in each of the rocker levers.
An object of the present invention is to provide a frame- o side bearing of the adjusting devices for changing the lever ratio of a two-armed rocker lever, particularly for transfer movements in a press by means of an arrangement of the bearing point of the rocker lever which is rigid during the operation.
This and other objects are achieved by the present invention which provides an arrangement for changing the lever ratio of a two-armed rocker lever, particularly for the transfer movements in a press. The rocker lever is pivotally connected in a lever arm and the starting movement is capable of being tapped by another lever arm. The arrangement includes a frame, a slide guide for the rocking bearing of the rocker lever, a control device and rotation transmission devices coupled to the control device. A nut-spindle connection is coupled to the rotation transmission device for the sliding movement of the slide guide relative to the rocker lever. The rocker lever, by means of the slide guide, is disposed in a pivot bearing of a support. The support is slidably guided in the frame. The support includes the nut of the nut-spindle connection for interacting with the spindle. The control device, rotation transmission devices and the spindle are arranged in the frame, and a device for the fixing of the position of the pivot bearing in the rocker lever is connected with the rocker lever in an operatively connected manner.
An advantage of the present invention is the possibility of changing the lever ratio in a defined position, for example, in the tool changing position. The mass that is required for this purpose is arranged close to the pivot bearing. The rocker lever is fixed in its pivot bearing. There are only slight deflecting movements in the longitudinal axis. The movement is not preset in a mechanically operated manner, for example, by means of an eccentric drive, but is cam-controlled. On the whole, the device is independent of its location in the press frame.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.